Semiconductor photocatalysis has received tremendous attention as a promising way for solving the worldwide energy and environment issues. Many efforts have been devoted to developing distinctive morphology and various semiconductor-based composite photocatalysts for enhancing photocatalytic activity in recent years. However, it is still a great challenge and imperative to profoundly understand the transfer mechanisms and to realize complete utilization of photoexcited charge carriers. This perspective for the first time highlights the inner impetus of the photogenerated charge carrier migration (band-band and Z-scheme transfers) over composite photocatalytsts. The notion of relative p-n junction for photocatalysis and the corresponding design principle of Z-scheme photocatalysts are introduced first. Then, simultaneous utilization of photogenerated electrons and holes for photocatalytic selective redox syntheses in one reaction system is recommended. The proposed reaction systems have characteristics of the environmentally friendly, atom economy, synergistic effect and high efficiency. Finally, the challenges and opportunities of photocatalysis are outlined and a perspective is given. We hope that the perspective review could give an inspiration for the fundamental research and guide the research direction of photocatalysis. Display omitted •The notion of relative p-n junction for photocatalysis was proposed.•The Judgment model of direct Z-scheme transfer was established.•The reaction systems of simultaneous utilization of photogenerated carriers were recommended.•The challenges and opportunities in the field of photocatalysis were suggested.